Whooping cough (pertussis) is an infection of the respiratory system caused by the bacterium Bordetella pertussis (or B. pertussis). It's characterized by severe coughing spells, which can sometimes end in a "whooping" sound when the person breathes in.
It mainly affects infants younger than 6 months old before they're adequately protected by immunizations, and kids 11 to 18 years old whose immunity has started to fade.
Before a vaccine was available, pertussis killed 5,000 to 10,000 people in the United States each year. Now, the pertussis vaccine has reduced the annual number of deaths to less than 30. But in recent years, the number of cases has started to rise. By 2004, the number of whooping cough cases spiked past 25,000, the highest level it's been since the 1950s.
The first symptoms of whooping cough are similar to those of a common cold:
After about 1 to 2 weeks, the dry, irritating cough evolves into coughing spells. During a coughing spell, which can last for more than a minute, the child may turn red or purple. At the end of a spell, the child may make a characteristic whooping sound when breathing in or may vomit. Between spells, the child usually feels well.
Although many infants and younger children who become infected with B. pertussis will develop the characteristic coughing episodes and accompanying whoop, not all will. And sometimes infants don't cough or whoop as older kids do. Infants may look as if they're gasping for air with a reddened face and may actually stop breathing (called apnea) for a few seconds during particularly bad spells.
Adults and teens with whooping cough may have milder or atypical symptoms, such as a prolonged cough (rather than coughing spells) or coughing without the whoop.